1. Field of the Invention
The present invention relates to a method for producing a single crystal diamond film. In particular, the present invention relates to a method for producing a single crystal diamond film having good crystallinity, a smooth surface, and good electrical and optical characteristics.
2. Description of the Related Art
Diamond has a large forbidden band width, a large electron mobility, a large hole mobility, a large saturation electron mobility, a large thermal conductivity, a low dielectric constant and high clarity. Therefore, the diamond is highly expected as a material for semiconductors, for example, semiconductive elements having heat resistance and radiation resistance and high speed high output semiconductive elements, and as an element for emitting blue light or UV light.
Recently, R. Mania et al proposed a method for synthesizing diamond in a vapor phase which comprises decomposing and exciting a raw material comprising a hydrocarbon gas such as methane with radiofrequency discharge (R. Mania et al, Crystal Research and Technology, 16, 785 (1981)).
The semiconductor field requires not only a diamond single crystal having high purity and crystallinity, but also one that has good crystallinity and contains a suitable amount of a certain impurity (dopant) with which valence electrons can be controlled.
It was confirmed that the single crystal diamond film can be grown on a diamond single crystal which has been synthesized under ultra-high pressure and that when the single crystal diamond is doped with an impurity such as boron acts as a p-type semiconductor (N. Fujimonri et al, Vacuum, 36, 99 (1986)).
When the impurity is doped by a conventional method for growing a single crystal diamond film by using a hydrocarbon gas and a hydrogen gas, a surface in, for example, the (110) plane has large irregularity so that the diamond crystal abnormally grows on the (110) plane. With respect to the electrical characteristics of the semiconductive element, when a Schottky diode is fabricated, it has a large reverse direction leak current.